This project compares, in rats, the presence to fasting of uremic and control rats. The substrate used during fasting as measured by VO2 and RQ, and the level of substrates - glucose, free fatty acids, lactate, hydroxybutyrate and alanine are measured after 24 and 36 hour fasts in 90% nephrectomy rats. Alanine and 6-C glucose turnover rats will also be compared between the two groups. Glucose, amino acid and free fatty acid net exchange between muscle and perfusion fluid will be determined in hemicorpus preparation from fasting uremic and control rats. A dose response curve between insulin and muscle protein synthesis and degradation will determine whether insulin control of protein synthesis is affected by uremia. A similar dose response curve between epinephrine and protein synthesis and degradation will be done to look for a comparable effect of uremia upon catecholamine effect.